1. Field of the Invention
The present invention relates to a method for producing a multilayer printing plate. More particularly, it relates to a method for producing a multilayer printing plate of excellent quality having high accuracy using a light-sensitive printing plate material having high light sensitivity comprising a silver halide emulsion.
2. Description of the Prior Art
Heretofore, bimetal plates and trimetal plates have often been utilized as multilayer printing plates. These multilayer printing plates comprise two or more metals, and the metal at the image area is different from the metal at the nonimage area. Further, these metals have differing receptivities to oil (ink) and water (dampening water) to provide a printing plate comprising an image area and non-image area. Various types of multilayer printing plates are known, depending on the combinations of metals, processes for printing plate making, and the printing plate structure (e.g., litho-relief, deep etch). The most typical metal for the image area (oleophilic metal) is copper, though brass, iron and silver, etc. have also been used. Typical metals for the non-image area (hydrophilic metal) are chromium, aluminum, nickel and stainless steel, etc.
In practice, a bimetal copper-chromium combination plate has been widely used. The copper-chromium bimetal printing plate is produced by image-wise exposing and developing a light-sensitive compositon coated on the chromium metal layer of a laminate of chromium and copper to form an etch resistant relief image on the chromium metal layer, removing the chromium metal layer at the non-relief image area to uncover the copper metal layer using an etching solution, and removing the refief image.
Examples of trimetal plates are iron-copper-chromium, zinc-copper-chromium, aluminum-copper-chromium, stainless steel-copper-chromium, etc.
However, light-sensitive compositions such as diazo resins, chromium resists (e.g., dichromate-gelatin, dichromate-polyvinyl alcohol, dichromate-gum arabic, etc.), etc., used for the production of these bimetal or trimetal printing plates have an extremely low sensitivity so that the plate making time is long and, accordingly, the cost is high.